Mine props



Oct. 20, 1970 MINE PROPS Filed April 3, 1968 R. BORE 3,535,071 v United States Patent 3,535,071 MINE PROPS Raymond Bore, 61 Rue des Ireelaude, 42 Saint Etienne, France Filed Apr. 3, 1968, Ser. No. 718,458 Claims priority, application France, Apr. 3, 1967,

Int. 01. 1521a 15/54 US. Cl. 248-357 2 Claims ABSTRACT OF THE DISCLOSURE A mine prop in the form of an extensible jack having laterally extending flanges secured to the lower end of the jack, and a shoe having internal projections for engagement with the laterally extending flanges to raise the shoe when the jack is contracted.

The present invention relates to improvements to props used in mines to support the roof and it aims at providing a prop of which the lower shoe may be able to be raised by the contraction of the prop, mainly in order to facilitate the fitting up or the repair of a support pier.

According to this inveition in a mine prop of the type which includes an extensible jack the lower end of the jack has laterally extending flanges adapted to engage with corresponding internal projections on a shoe so that contraction of the jack causes lifting of the shoe by engagement of the flange with the projections.

Preferably two semi-cylindrical straps are clamped to the lower end of the jack body, each strap carrying a laterally extending flange with an arcuate profiled upper surface for engagement with a projection on the shoe. It is also preferred that the shoe has two I section longitudinal members, the upper internal flanges of which provide the shoe projections.

A mine prop in accordance with the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a vertical section of the lower part of a prop,

FIG. 2 is an elevation, partly in section along the line 11-11 of FIG. 1, showing a support pier made with props according to the invention, and

FIG. 3 reproduces FIG. 2 with one prop in the contracted position.

In FIG. 1 there is shown at 1 the body of the jack of a mine prop according to the invention. In known manner, the body 1 is supported by a lower plate 2 provided with a hemi-spherical boss 211 so as to form a ball-and-socket joint in order to allow the free positioning of the jack with respect to the ground. There is associated with the body 1 a sliding stem 3 (FIG. 2) of which the upper end, or head, is secured to a support heading 4. This heading 4 is supported by two props which may form part of a pier in which two other props hold up a second heading.

The thrust plate 2 is fitted inside a lower shoe 5 made in the form of a casing, of which the side walls, placed longitudinally in relation to the axis of the heading 4, are constituted by I sections 5a (FIG. 1). The upper side flanges of these sections 5a are spaced to give a considerable clearance for the passage of the base of the jack 1,

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the inside edges of the said flanges being chamfered, as shown at 5b.

There is also fixed to the base of the jack body 1 a collar composed of two straps 6 of semi-circular section, joined together by two pairs of bolts 611. Each of these straps 6 has fixed radially to it a flange or stop 7 of a curvilinear triangular profile, it being noted that the edge of this flange 7 which is turned towards the chamfered edge 5b of the sections 5a has a profile of the arc of a circle of which the centre coincides with that of the hemispherical boss 2a of the thrust plate 2.

It will be realised that because of their profile the flanges 7 leave the prop free to take up any direction in relation to the shoe 5. On the other hand, as shown in FIG. 3, when one of the two jacks 1-3 associated with each heading 4 is contracted, the lower body 1 moves axially upward, carrying with it the corresponding shoe 5, the flanges 7 coming to bear against the upper flanges of the sections 5a. The surface of the ground which forms the support for the shoe in question may thus be smoothed, or the lower face of the shoe may be reached, for example for repair.

It will be appreciated that there may be any number of the flanges 7. In the same way, in place of the I sections 5a, the upper part of the shoe may carry a horizontal plate pierced by an opening shaped to work in conjunction with the flanges fixed to the base of the jack.

It must moreover be understood that the preceding description has been given only by Way of example, and that it does not limit the scope of the invention which will not be avoided by replacing the constructional details described by any other equivalents.

I claim:

1. A mine prop comprising an extensible jack, laterally extending flanges secured to the lower end of said jack, a shoe having internal projections for engagement with said flanges whereby said shoe is raised when said jack is contracted, and two semi-cylindrical straps clamped to opposite sides of said jack, each of said straps carrying a laterally extending flange with an arcuate profiled upper surface.

2. A mine prop according to claim 1, wherein said shoe has two I section longitudinal members disposed so that the upper internal flanges of said I sections can engage on said arcuate profiled surfaces of said flanges.

References Cited UNITED STATES PATENTS 898,336 9/1908 De France 254-101 1,268,410 6/1918 Weber 254 101 XR 1,722,312 7/1929 Roos 248357 FOREIGN PATENTS 729,805 5/1955 Great Britain. 1,002,038 8/1965 Great Britain.

ROY D. FRAZIER, Primary Examiner A. FRANKEL, Assistant Examiner US; Cl. X.R. 254101 

